Apparatus for the production of music



July 9, 1935. B, F. MiESSNER 2,007,302

APPARATUS FOR THE PRODUCTION OF MUSIC Filed March 1934 2 Sheets-Shect 1 INVENTOR ATTORNEY.

July 9, 1935; B. F. MIESSNER 7, 0

APSPARATUS FOR THE PRODUCTION OF MUSIC File d March 7, 1934 2 Sheets-Sheet 2 INVENTO Patented July 9, 1935 UNITED STATES PATENT OFFICE Benjamin F. Miessner, Millburn Township, Essex County, N. J., assignor to Miessner Inventions, Inc., a corporation of New Jersey Application March 7, 1934, Serial No. 714,385

18 Claims. (01. 84-246) This invention relates to the production of music from tuned vibrators, and more particularly to improved means and methods for exciting the vibrations of such vibrators. As to certain of its subject matter this application is a continuation in part of my co-pending application, Serial Number 662,697, filed March 25, 1933.

In the tuned vibrator type of musical instrument a commonly employed method of setting each vibrator into vibration is impulse excitation-e. g., the stroke of the hammer in the playing of the piano, the pluck of the plectrum in the playing of the mandolin,'etc. It is a broad object of the instant invention to provide improved means and methods for impulse excitation of the vibrators.

The use of electrical or electrically controlled means for exciting the vibrators has certain advantages, such for example as the opportunity to locate the vibrators remotely from the playing keys or the like, and various such excitin means are known. It is an object of my invention, however, to provide improved such means for impulse excitation of the vibrators.

An opportunity for effective control over output tone quality in respect of inception and damping characteristics is afforded by the selective availability of impulse and oscillatory excitation of the vibrators It is a further object of my invention to provide simple and economical means for selectively producing impulse and oscillatory excitation of the vibrators.

It is known that characteristics of the excitation, whether impulse or oscillatory, aifect various qualitative characteristics of the vibrator vibration and output sound aside from those of inception and damping. It is an object of my invention to provide improved excitation control means and methods whereby to effect control over such qualitative characteristics of the output sound. A more specific'object is the provision of improved excitation control means whereby to effect control over the timbre, or harmonic structure, of the output sound.

A general object is the provision of an improved instrument whereby output tones of a variety of qualitative characteristics may be produced.

Other and allied objects will more fully appear from the following descriptionand the appended claims.

In such description reference is had to the accompanying drawings of which:-

Figure l is a partly perspective, partly diagrammatic view of one embodiment of my invention in simple form;

Figure 2 is alike view in slightly modified form;

Figure 3 is a partly perspective, partly diagrammatic view of my invention in more complete form and adapted effectively to control the timbre of the output sound;

Figure 4 is a like view in somewhat modified form; and

Figure 5 is a partly cross-sectional, partly diagrammatic view of another embodiment of my invention; and

Figure 6 is a like view of a further embodiment of my invention.

It is well known that vibrator exciting forces may be translated from electric currents, such a current energizing an exciting device immediately associated with the vibrator-for example an electromagnet which directly attracts the vibrator or which moves a hammer or the like to strike the vibrator. When such translation is employed in simple impulse excitation only that flow of electricity which immediately ensues the inception of flow is useful, and the continuation of flow for any appreciable length of time is wasteful and usually detrimental. Thus the continuation of flow through such an electromagnet as abovementioned tends to cause heating thereof and compels its design in far more generous proportions than are required to withstand the limited useful portion of the flow. It is therefore desirable to energize the electromagnets or the like by a flow of electricity of automatically limited duration.

In my application Serial Number 637,403, filed October 12, 1932, now Patent 1,979,633, granted October 31, 1933, I showed electromagnets moving hammers adapted to strike the strings; the current energizing the electromagnets being generated by magneto-electric generators attached to, and operated only by movement of, the playing keys. The playing keys being capable of only limited movement, the desired limitation of current duration was obtained. It is frequently desirable, however, that the keys function only to control, and not to generate, the current or flowlof electricity, the latter itself being derived from a continuously operative source. The present invention accordingly comprehends several embodiments wherein the exciting devices immediately associated with the vibrators are energized by thefiow, of limited duration, of electricity derived from such a source.

In the first-illustrated of these embodiments there is employed an electrical capacity adapted condenser 3.

to store a predetermined quantity of electricity from the source, the exciting device immediately associated with the vibrator being energized bythe flow of that quantity of electricity into or out of the condenser. This is illustrated in Figure 1. Herein the vibrator isshcwn as the tuned string I, strung for example over triangular bar 2 and bridge I!) between tuningand hitch-pins not herein necessary to show. This figure by way of example shows the bridge I secured to a soundboard ll, providing direct mechanicoacoustic' translation of string vibration into sound; The exciting means immediately associated with the string is'shown as the electromagnet 4 positioned in slight spaced relationship thereto; the electrical capacity is shown as the Between a first end of the condenser and a first end of the electromagnet is illustrated the switch comprising the blade 5' and the contact 5", which switch may be keycontrolled and is biased to an open position. The second end of the capacity 3 is shown connected to ground, which is a convenient designation for a first terminal of the battery or other source of electricity 6. The second end of the electromagnet is also connected-to ground, so that upon closing of the key-switch 5 the condenser and electromagnet will be connected in series and such quantity of electricity as may then be stored in the condenser will be discharged through the electromagnet. In order that the condenser 3 may normally have stored therein a quantity of electricity, the battery or other source 6 is connected through a resistance 1 tea contact 5" included in the key-switch 5 and arranged to be impinged against by the switch blade 5' when the switch is open. The voltage of the source 6 will determine the quantity of electricity stored in the condenser 3; and if desired this quantity may be regulated by the potentiometer 9 included in association with the source 6 for regulation of its efiective voltage.

The illustrated connection of condenser 3 to ground is through a; switch II. This may be thrown if desired to the left to connect the condenser to ground through the source 6. Under these conditions the condenser is maintained normally discharged of electricity and will be charged with the predetermined quantity upon closing of the switch blade 5' against the contact 5". The action is entirely similar to that occurring with switch I! in the illustrated position, excepting for the immaterial opposition of direction of flow through the electromagnet and for the fact that the flow now must pass through the eifective internal resistance of the source 6.

In series with the electromagnet 4 is illustrated a variable resistance 8. It is convenient to denote by the symbol R the sum of the value of this resistance 8 and the residual resistances of the circuit closed by closing of the key-switch 5- i. e., theeifective internal resistance of the electromagnet, and the effective internal resistance of the source 6 if this is rendered in series with the condenser 3 by throwing of switch I! to the, left. The characteristics of the flow of electricity occurring upon closing of the key-switch 5 will be determined by the relative values of R, of the capacity of 3, and of the inductance of 4. Thus if R be less than a critical value of 2L (1- (L being the inductance of 4 in henries and C the capacity of 3 in farads) the flow will be of an oscillatory nature; otherwise it will be aperiodic. When the flow is oscillatory it consists in a train of oscillations whose frequency, initial amplitude and rate of decay depend on the men-, tioned values; when aperiodic it consists in a single current pulse which rapidly rises to a maximum value and then decays, the maximum value,

the rate of arrival thereat, and the rate of decay therefrom being determined by the mentioned values.

For simple impulse excitation I employ suiiicient resistance in 8 to render the fiow'aperiodici. e., to raise R to at least the critical value abovementioned. With the source 6 adjusted to any given voltage output, and with fixed inductance and capacity values of 4 and 3, respectively, the maximum impulse excitation will be obtained when R is of such critical value. An increase from this value, as by the increase of the resistance of 8,provides a convenient means of control whereby to reduce the strength of the impulse excitation.

Excitation of a modified nature is obtained if R be made appreciably less than the critical value, either by reduction of the value of 8 or by .its complete short-circuiting as by the switch I8 shown connected therearound. In this event the fiow upon closing of the key-switch 5 will be oscillatory and its frequency may be tuned by variation of L or C, the condenser 3 having been illustratively shown variable. The excitation of the, string produced by the flow will then of course beoscillatory and will (assuming the electromagnet d to be unpolarized) be bicyclic with respect to the flow. Therefore if the flow be.

alternating current of the strings own frequency.

The distinction lies in the damped nature of the flow in the instant case, and may of course be minimized by making as low as possible the residual resistance of the circuit. The switch l8 will thus be seen to provide a very convenient means for selecting between impulse and oscillatory excitation.

It has thus far been assumed that the electromagnet 4 is unpolarized. It should be understood, however, that in the carrying out of my invention the electromagnets may if desired be permanently polarized, as by permanent magnetization of the core 4' of the electromagnet 4 of Figure 1. Preferably in such case the permanent polarization should be of at least the effective strength attained at peak by the temporary polarization resulting from the above discussed flow of electricity through the electromagnet. It is to be noted that with the electromagnet so polarized an oscillatory flow of electricity therethrough will produce an excitation which is cyclic, rather than bicyclic, with respect to the flow.

In Figure 1 the electromagnet 4 is of simple form with fixed core 4 and is intended to influence the string by magnetic induction. In Figure 2, however, I have alternatively illustrated an electromagnet 6 having a movable core 4" adapted to be moved upwardly by the electromagnet upon the fiow of electricity through the latter and therefore to impinge against the string and excite the same by mechanical impact. The core 4 may be surmounted by a tip 4" of rubber or the like, forming a hammer head suitable for such impact. The electromagnet upon energize.- tion thereof tends to centralize the core 4" verti- I charge or charge current. plurality of strings I, in order that the circuits for a complete instrument may be indicated. For

cally therewithin; the core, being normally maintained as by gravity in a lower than centralized position, is moved upwardly by the energization and caused by its momentum to overshoot such centralized position and strike the string. In this case in which the core of the electromagnet is movable and intended mechanically to influence the string, the resistance 8 should be maintained at at least a sufllciently high value to insure a periodicity of the flow through the electromagnet. It may as before, however, be increased from this value to reduce the strength of the excitation. For maximum efliciency the principal portion of the flow should occur before the core 4" in its upward movement has passed a centralized position within the electromagnet.

It will be appreciated that while a specific arrangement has been shown in Figure 1 for maintaining the condenser in readiness to produce the flow through the electromagnet (i. e., normally charged or discharged, according to the position of switch l'l) other arrangements may be employed. Thus in Figure 2 I have illustrated one wherein the resistance 1, instead of being connected to a separate contact 'on the keyswitch 5. is connected to the blade 5' of that switch. With this connection the desired normal condition of the condenser 3 is obviously maintained while the key-switch 5 is open. When the key-switch is closed the condenser will as before produce the flow through the electromagnet; there will also then take place through the electromagnet, however, a steady current determined by the voltage of battery 6 (as adjusted by potentiometer 9) and the combined resistance value of 'l and R. In order to reduce the magnitude of this steady current the resistance value of I may be made as high as consistent with satisfactory rapidity in attainment of normal condition by condenser 3 upon opening of the keyswiteh 5.

In Figure 3 I show a more elaborate string excitation system, again employing condenser dis- The figure shows a each string there may be provided a separate condenser 3; each of these may be maintained normally charged or discharged, and discharged or charged (as the case may be) at will through the string exciting circuit, by a resistance 1 from the voltage source 6 and by a key-switch 5, as in Figure 1.

The string exciting circuit for each string is provided with a plurality of branches, an electromagnet being included in each branch of each such circuit. Thus the contact 5" of the switch for each string is shown connected to both an electromagnet 4a and an electromagnet 42), these electromagnets being positioned adjacent respectively different portions of that string. In series with each electromagnet 4a and 4b is an individual resistance 8a and 8b, these resistances being in each case preferably of just sufficient value to insure aperiodicity of flow upon closing of the switch 5; it will be understood that if desired these resistances may be made inherent in the windings of the respectively associated electromagnets.

All the electromagnets 4a are connected to ground through the common resistance l3a; similarly all the electromagnets 4b are connected to ground through the common resistance l3b. Each of these resistances is preferably variable from a low or zero value to a relatively high value.

Their function is the regulation of the relative strengths of excitation effected by the respective electromagnets 4a and 4b of any string whose associated key 5 is depressed. Such regulation makes possible simultaneous impulse excitations, at different points along the string, of controlled relative strengths.

' It is well understood that when a string is excited by impulse excitation the form of its vibrationi. e., the relative amplitudes and phases of its diiferent partial vibration components-is determined by the point along the string whereat the excitation is effected. Thus if any of the strings I be at one time excited essentially by only the associated electromagnet 4a (the resistance l3b being adjusted to a relatively high value) and at another time be excited essentially by only the associated electromagnet 4b (the resistance l3a being adjusted to a relatively high value), its vibrations in these separate cases will be of re spectively different form; each partial vibration component will occur in a respectively different amplitude and phase. If the string be subjected to simultaneous excitation at full strength by each of the associated electromagnets 4a and 4b (the resistances 13a and l3b being adjusted to their minimum values), each partial component in the ensuing vibration will be of a new amplitude (as well as phase), its amplitude at any instant being the algebraic sum of the amplitudes at that instant of that partial in the separate vibrations abovementioned; a new vibrational form results. Further if the string be subject to simultaneous excitation at different fractional strengths by each of the associated electromag nets (the resistances [3:1 and I3!) being adjusted for example to respectively different values) each partial component in the ensuing composite vibration will be of still a new amplitude. (as well as phase), since its instantaneous amplitudes are determined by the algebraic addition of modified separate instantaneous amplitudes. While I view only the relative amplitudes (and not phases) of the several partial components as being of particular importance in the composite vibration, the differences in phase as well as amplitude of each one component in the respective separate vibrations are of great importance in producing distinctive differences in relative amplitudes in the composite vibration.

It will be understood that the number of separate electromagnets which may be employed with each string is not limited to two, and that still greater variations in relative amplitudes of the several partial components in the composite vibration may be produced by the use of a greater number of electromagnets with individual excitation strength control.

Another method of extending the range of possible variation of relative partial amplitudes in the composite vibration lies in the control of direction, as well as of strength, of the excitation prcduced by one or more of the electromagnet-s associated with each string. It will be understood that this provides phase control over all the partial components in the separate vibration resulting from excitation by that electromagnet. A non-limitative example of means for controlling this direction has been illustrated in Figure 4. Herein each electromagnet 4b is complemented by another electromagnet 4b in spaced relation to the same string portion but on the opposite side of the string. A terminal of each electromagnet 4b' is connected to a terminal of the associated electromagnet 4b and to the key-switch 5 through the resistance 8b. The other terminals of all the electromagnets 4b are connected together and tea first extremity of the potenti ometer l3b', which is substituted for the resistance I3b of Figure 3. The other terminals of all the electromagnets 4b are connected in common to the other extremity of the potentiometer I317. The movable contact l3b" of the potentiometer is connected back to ground, as was the lowershown extremity of the resistance l3b of Figure 2. The operation of the electromagnets 4b and ib and of their associated control is now as fol lows:

If the movable contact l3b" is adjusted to the center of the potentiometer I31) there will flow, upon closing of the switch 5 associated with any string I, equal quantities of electricity in the associated electromagnets 4b and 412'; these electromagnets are, mutually similar and arranged upon similar energization to urge the string equally in opposite directions. Therefore the effective excitation of the string by these electromagnets in combination is zero. But as the contact l3b" is moved toward either extremity of the potentiometer l3b the energization, upon closing of any switch, of the electromagnet connected to that extremity is increased and that of the other reduced, and the strength of excitation by the combination therefore increased from its zero value. The same is true for movement of the contact toward the other extremity; but obviously the direction of excitation will in this case be opposite. Thus in the illustrated arrangement the potentiometer l3b, and in particular its contact l3b", provides the desired control of excitation direction for the electromagnet combinations 4b4b'; at the same time it provides a very satisfactory control of excitation strength alternative to the previously illustrated control. Such'an arrangement may of course be employed with other or all of the electromagnets, being illustrated with the electromagnets 4b only by way of example.

. In Figure 4 I also show a further feature of my invention, which includes the selective use of the same electromagnets for impulse or sustained oscillatory excitation of the strings. Thus the. blades 5' of the several key-switches are normally--i. e., for impulse excitationconnected to the respective condensers 3 through the inthrown at will to disconnect the switch blades 5' from the condensers 3 and to connect them each to a terminal of a respective generator it, the other terminals of which generators may be connected together and to ground. e generators I6 may be of any suitable form to generate electric oscillations, in each case preferably of a fundamental frequency coinciding with that of the associated string. Such generators themselves, and their use in connection with electromagnets to vibrate the strings, are well known and are therefore not herein described in detail. In the combination illustrated not only are the same electromagnets employed for both types of excitation, but the same playing meansi. e., key-switches 5-and the same vibrational form control means-e. g., resistance [to and potentio'meter l3bare employed in the'two cases.

The oscillatory excitation just outlined differs from the oscillatory excitation obtained in the circuit of Figure 1 with switch It closed in that it is sustained rather than damped. For string vibrations of relatively short duraflon this dis tinction is not of great importance and the circuit of Figure 1 is to be preferred on the ground of simplicity. If string vibration of relatively great duration at substantially constant ampli tude is desired, however, the circuit of Figure 4 is to be preferred.

It is to be noted that when the string is oscillatorily excited the harmonic structure of its vibration with any given setting of the controls (l3a and l3b) will not necessarily be similar to the harmonic structure resulting from impulse excitation with the same control settings; these controls, however may still be employed with the oscillatory excitation to produce significant changes of harmonic structure of the vibration.

In Figure 4 I show mechanico-electro-acoustic translating apparatus for translating the string vibrations into sound; the strings I are therefore in this figure shown passing over a second triangular bar 2' instead of over the bridge 10 of Figure 1. This bar 2' is intended to be electrically conductive, and thus forms an electrical connection to each of the strings I. Adjacent and in slight spaced relationship to the several strings I is provided a conductive strip 20 of small cross-section. This may be cemented to an edge of an insulating strip 2! and this secured in any convenient manner in position to maintain the conductive strip in the mentioned relationship to the strings. Obviously a small capacity is formed between the conductive strip 20 and each of the strings; and these several capacities in parallel with each other form a total capacity from strip to strings. In this total capacity may be maintained a charge relatively in capable of rapid variation. For this purpose the strip 26 is connected through a high resistance 22 to one terminal of a high voltage battery or other source 30, the strings (through the medium of the bar 2') being connected to the other terminal of the battery. If now any string be vibrated toward and away from the conductive strip 20 the total capacity above mentioned will be varied. By virtue of the relative constancy of the charge therein the voltage thereacross will vary in accordance with the frequency and. waveform of the string vibration, and the voltage across the high resistance 22 will similarly vary.

For responding to voltages across the resistance 22 there is provided a thermionic vacuum tube 25. The cathode'of this tube may be energized in any suitable manner; its anode current may be supplied as from a battery or other source 3|; and its cathode may be maintained at a potential slightly positive with respect to the negative terminal of source 3| by the flow of anode current through condensively-by-passed resistance 26. The grid of tube 25 may be biased slightly negative with respect to the cathode by connection thereof through the high resistance or grid leak 24 to the negative terminal of source 3!. The resistance 22 is connected through the condenser 23 across the grid leak 24.

In the output circuit of tube 25 may be connected in cascade amplifier 21, potentiometer 28 and loudspeaker 29. Electrostatic shielding schematically shown as 32, may advantageously be provided at least partially around the strip 20, resistances 22 and 26, tube 25, and immediately associated elements. Obviously electric oscillations appearing across resistance 22-i. e., translated from string vibration-will be amplified by tube 25 and amplifier 21, may be controlled in respect of amplitude by potentiometer 28, and are translated into sound by loudspeaker 29.

In the spring exciting systems shown in Figures 1 through 4 the condenser forms a means for limiting the flow of electricity through the electromagnet. In other embodiments of my invention, however, other means for producing this effect are employed, and one such means is illustrated in Figure 5. This means is part of a flow control system including the key 4|, and comprises a variable resistance of value which is normally high and is momentarily reduced upon key depression. The key 4| is pivoted as at 42 and has the rearward extension 4| weighted so as normally to rest on felt 43. The key is depressible to raise the extension 4| and impinge the same against the stop 44. Above the key extension 4| is provided the variable resistance element comprising the pile 48 of discs of carbon or other resistance material, the pile normally having a very high or preferably infinite resistance. It may be retained in the vertical hole 49 in insulating block 50, resting on the plunger 5| which in turn is normally supported in position just entering the bottom of hole 49 by the leaf spring 52 secured to the bottom of the block 50. To the block 50 and across the top of the hole 49 may be secured a conductive plate 53. When the plunger 5| occupies its normal position the pile 48 is in no compression and its top is preferably in very slightly spaced relationship to the bottom of plate 53; its resistance is therefore infinite. If the plunger 5| be raised, however, the top of the pile 48 will be raised into contact with the stationary plate 53 and the pile placed in compression and its resistance thus lowered.

The upward movement of the key extension 4| is intended to raise the plunger 5|. In order, however, to render this raising momentary only the stop 44 is arranged to prevent impingement of the key extension against the plunger, and there is interposed between the key extension and the plunger a weight 45. This is normally carried by the key extension; but upon impingement of the latter against stop 44 the momentum of the weight. causes it to continue its upward motion and momentarily to raise the plunger 5| and compress the pile 48. In order that the weight may invariably return to the same position relative to the key extension, it may be connected to the latter by a light leaf spring 46, which in turn is secured to' an upward boss 4|" formed from the extension 4|. Felt 41 may be provided on top of the extension 4|, and the spring 46 may normally bear thereagainst,,the felt serving to suppress tendencies of thqspring and weight to oscillate with respect to the extension. For electrical terminals of the variableresistance element there may be employed the plate 53 and the spring 52. In series therewith may be connected the source 6, with its potentiometer 9 if desired, the electromagnet 4 and the resistance 8. The last now serves only as a control of excitation strength, over andabove: such control as may be effected by key velocity as hereinafter mentioned.

Illustrative of a slightly modified arrangement for influencing the string by the electromagnet 4 I have shown the electromagnet in Figure '5 again provided with a fixed core 4', but arranged upon energization to attract an armature 55 secured to the pivoted shank 58 of the hammer 51. This attraction moves the hammer shank about its pivot 58 and the momentum thus imparted to the hammer moves the same into contact with the string. By the time of such contact the pile 48 will have re-assumed a substantially infinite resistance and no substantial attraction of electromagnet for armature will remain, wherefore the hammer will rebound back to its normal or illustratedposition wherein the shank 58 rests against the felted stop 59.

An important feature of this embodiment of my invention resides in its responsiveness to touch, or key velocity. It will be obvious that variations in this velocity will produce variations in the momentum of the weight 45, and therefore in turn variations in the degree of compression of the pile 48, and of the speed and value with and to which its resistance will be reduced. Accordingly the current supplied to the electromagnet is of an amplitude and a rate of rise each greater the greater the key velocity, and the strength of hammer blow on the string is thus responsive to touch.

In Figure 6 I show another embodiment of my invention also adapted for touch responsiveness. The key 4| is provided, as in Figure 5. Further as in that figure a weight is employed, this being shown however as the electrically conductive weight supported by the light leaf spring 46' to the insulating bushing 62 on block 58. With the key in its normal position the weight 45' is lightly urged by the spring-46 against felt 6| secured to the top of the key extension 4|. On the top of the weight 45' is formed a contact but ton 45". Above this button is another contact button 52" formed on the. spring 52, which is secured to the block 55. The height of the second contact button 52 is such that a slow depression of the key 4| and raising of itsextension 4| into impingement against the stop 44 will raise the weight 45. and the contact button 45" into a position slightly short of contact with the button 52". If the key be depressed with any appreciable velocity, however, the weight 45', upon impingement of the extension 4| on the stop 44, will continue its upward motion and bring the contact button 45 into contact with the button 52". Thereupon the spring 52 will be temporarily flexed upwardly in a degree increasing with the velocity of the key depression, the two buttons remaining in mutual contact during the period of this flexure. This period of course depends on the degree of flexure and hence on the velocity of key depression.

Viewing the contact buttons and their supporting springs as constituting a switch, it will be obvious that upon key depression this switch is closed for a period dependent on the velocity of the depression. The switch is serially connected between the battery 6 and the electromagnet 4,

and the latter is therefore energized while the switch is closed. In this embodiment the electromagnet is illustrated, as in Figure 2, as having the movable core 4" surmounted with the ham-- mer' head 4". The period during which the switch remains closed in response to key depression of substantially maximum possible velocity is preferably not in excess of the time interval required for the core 4" to rise to a centralized position in the electromagnet in response to that depression, since the continuance of flow of electricity after the core has reached this position is a deterrent and not an aid to impingement of the hammer head 4" against the string. If this limitation be observed it will be appreciated that as key velocity is reduced from maximum, the'attendant reduction of period during which the switch remains closed will'produce. a corresponding reduction in the integrated force applied to the core 4 and hencein the strength of the impact of hammer head 4 on the string.

. spaced relationship to the string I.

While Figures 5 and 6 are fundamentally adapted to use with any form of vibration-sound translation, I have shown therein the conductive strip 20, supported by the insulating strip 2|, in The string 20 may be electrically connected to the elements 22 and 23 ilustrated in Figure 4, thereby providing *mechanico-electro-acoustic translation of string vibration into sound.

I particularly prefer vibration-sound transla-.

tion. In the case of direct mechanico-acoustic translation--e. g., as illustrated by the soundboard II in Figure l-energy exceeding that of the sound to be produced by a given string must be passed into or out of the associated condenser 3 upon closing of the switch 5. No such requirement exists in the case of the mechanico-electroacoustic translation-e. g. as illustrated in Figure 4because the sound energy is supplied by the amplifier 21, being controlled rather than produced by the string. Indeed, with mechanicoelectric translating apparatus operating on the basis of inductive infiuencement by the string of an adjacent member-in Figure 4 the conductive strip 20-substantially no energy is lost by the vibrating string other than that required to overcome the self-resistance of the string to vibration; the translating apparatus is influenced solely by the displacement and not by the force of the string. In such cases it is unnecessary to employ strings of high mass at high tensions; and in order that the maximum displacement be produced by excitation of a given strength I prefer to employ strings I of relatively low mass held under relatively low longitudinal tension.

As to the various arrangements which I have shown of the electromagnet 4 with respect to the string l, these are 1 in general interchangeable, subject to the limitation that the arrangement shown in Figure 1 (and embodied in Figures 3 and 4) is intended for use when an oscillatory flow takes place through the electromagnet.

While the strings I represent a preferred form of vibrator, my invention is obviously not limited thereto, as any form of tuned vibrator may obviously be substituted therefor. As to the principles of operation of the'plurality of electromagnets opposite respectively diiierent portions of the vibrator, however, these are'in general applicable only to vibrators whose vibrational forms in diiferent portions are inherently different. It is of course obvious that in cases wherein the string or other vibrator is directly attracted by the electromagnet 4 it must be of steel or other magnetic material; and further that in cases wherein the particularly illustrated mechanicaelectro acoustic translation is employed the strings or other vibrators should be electrically conductive.

It will be understood that while I have described my invention in terms of specific embodiments thereof, I intend that the scope of the invention be not limitedby the details of these embodiments, but rather gauged by the following claims.

I claim:

1. In a musical instrument including a tuned vibrator: impulse exciting means for said vibrator comprising an electrically operable exciting device associated with said vibrator, a source of electricity, electric flow control means connected with said source and said exciting device and operable at will ,to produce a flow through said exciting device of electricity from said source, and means included in said flow control means for limiting the duration of said flow.

2. In a musical instrument including a tuned vibrator: impulse exciting means for said vibrator comprising an electromagnet in spaced relationship to said vibrator, a source of electricity, electric flow control means connected with said source and said electromagnet and operable at will to produce a flow through said electromagnet of electricity from said source, and means included in said flow control means for limiting the duration of said flow.

3. In a musical instrument including a tuned vibrator: impulse exciting means for said vibrator comprising a condenser, means for normally maintaining said condenser in a given state of charge, an electrically operable exciting device associated with said vibrator, and means operable at will to produce through said device a predetermined change in the charge of said condenser.

4..In a musical instrument including a tuned vibrator: means for exciting said vibrator comprising a condenser, means for normally maintaining said condenser in a given state of charge, an electromagnet in spaced relationship to said vibrator, and means operable at will to produce through said electromagnet a predetermined change in the charge of said condenser.

5. In a musical instrument including a tuned vibrator: means for exciting said vibrator comprising a condenser; means for normally maintaining therein an electrical charge; an electrically operable exciting device associated with said vibrator; a normally open circuit serially comprising said condenser and said electromagnet; and means included in said circuit for closing'the same at will whereby to discharge said condenser through said electromagnet.

6. In a musical instrument including a tuned vibrator: means for exciting "said vibrator com-- prising a condenser; an electrically operable exciting device associated with said vibrator; a normally open circuit serially comprising said condenser, said'electromagnet, and a source of current; means included in said circuit for closing the same at will whereby to charge said condenser through said electromagnet; and means operative upon opening of said circuit to discharge said condenser.

7. In a musical instrument including atuned vibrator: exciting means therefor selective with respect to characteristics of the excited vibration, comprising a condenser; means for normally maintaining therein an electrical charge; an electromagnet in spaced relationship tosaid vibra-tor; a normally open circuit serially comprising said condenser, said electromagnet and electrical resistance; means included in said circuit for closing the same at will whereby to discharge said condenser through said resistance and electromagnet; and means for controlling the value of said resistance to control the nature of said discharge.

8. In a musical instrument including a tuned vibrator: exciting means therefor selective with respect to characteristics of the excited vibration,

comprising a condenser; means for normally maintaining said condenser discharged; an electromagnet in spaced relation to said vibrator; a normally open circuit serially comprising said condenser, said electromagnet, electrical resistance and a source of current; means included in said circuit for closing the same at will whereby to charge said condenser through said electromagnet; and means for controlling the value of said resistance to control the nature of'said discharge.

9. In a musical instrument including a tuned vibrator: means for exciting said vibrator comprising a condenser, means for normally maintaining said condenser in a given state of charge, a plurality of electromagnets in spaced relationship to respectively different portions of said vibrator, and means operable at w'll to produce through said electromagnets simultaneously a predetermined change in the charge of said condenser.

10. In a musical instrument including a tuned vibrator: impulse exciting means whereby said vibrator may be selectively excited into vibration of a plurality of different forms, comprising a plurality of electrically operable exciting devices respectively associated with a plurality of different portions of said vibrator; a source of electricity; electric flow control means connected with said source and said exciting devices and operable at will to produce a flow through said electromagnets of electricity from said source; means included in said flow control means for l miting the duration of said flow; and adjustable means respectively associated with said exciting devices for varying the relative portions of said flow respectively passing therethrough.

11. In a musical instrument including a tuned vibrator: means for exciting said vibrator selectively to vibration in a plurality of diiierent vibrationa1 forms, said means comprising a plurality of electromagnets respectively in spaced relationship to different portions'of said vibrator; means operable at will to passa current through said electroinagnets simultaneously; and adjustable means connected with the several said electromagnets for controlling the portions of said current respectively passing through the several said electromagnets.

12. In a musical instrument including a tuned vibrator, an electromagnet in spaced relation to a portion thereof, and means for passing a current through said electromagnet whereby to excite said vibrator into vibration: means for controlling the amplitude of said vibration comprising a second electromagnet in spaced relationsh p to said portion of said vibrator but on the opposite side thereof from said first electromagnet, means for passing a current through said. second, electromagnet simultaneously with the passage of current through said first whereby oppositely to excite said string; and means for controlling the relative amplitudes of said two currents.

13. In a musical instrument including a tuned vibrator: means for exciting said vibrator in controlled degree and direction comprising two elec= tromagnets in spaced relation to a single portion of said vibrator but on opposite sides thereof; means for passing simultaneous currents through said electromagnets in respective directions to create mutually opposing fields; and means for controlling the relative amplitudes of said cur rents.

14. In a musical instrument including a plurality of tuned vibrators: vibrator exciting means selective with respect to characteristics of the excited vibrations, comprising a plurality of electromagnets respectively in spaced relation to said vibrators; a plurality of playing switches respectively in serieswith said electromagnets; a plurality of sources of current pulses; a plurality of electric oscillation generators of frequencies respectively similar to those of said vibrators; and means selective with respect to said sources and said generators, for connecting either said pulse sources respectively or said generators respectively to said electromagnets and said playing switches.

15. In a musical instrument including a tuned vibrator; an electrically operable exciting device associated therewith, and a source of current: means for passing a current of limited duration from said source through said device, said means comprising a resistance electrically interposed between said source and said device, the value of said resistance being normally high and being reduceable in response to pressure on said resistance; a stop member; a key movable to produce impingement of a portion thereof against said stop member; and a weight normally carried by a portion of said key and adapted upon said impingement to continue movement and to impinge against and press upon said resistance.

16. In a musical instrument including a tuned vibrator, an electrically operable exciting device, and a source of current: means for passing a current of limited duration from said source through said device, said means comprising a key and a stop member therefor, said key being movable to produce impingement of a portion thereof against said stop member; a weight arranged for movement with said key until said impingement occurs and for further movement in response to its own momentum; and a normally open switch electrically interposed between said source and said device, said switch having a portion disposed in the path of said further weight movement and being adapted to be closed by and during impingement of said weight against said switch portion.

17. In'a musical instrument, the combination of a key and a stop member therefor, said key being movable to produce impingement of a portion thereof against said-stop member; a weight arranged for movement with said key until said impingement occurs and for further movement in response to its own momentum; a source of cur-- rent; and a current passing device disposed in the path of said further weight movement and responsive to impingement thereagainst of said weight.

18. In a musical instrument including a tuned vibrator, an electrically operable exciting device, and a source of current: means for passing a current of limited duration from said source through said device, said means comprising a key and a stop member therefor, said key being movable to produce impingement of a portion thereof against said stop member; a weight arranged for movement with said lrey until said impingement occurs and for further movement in response to its own momentum; and a current passing device electricall interposed between said source and said device, mechanically disposed in the path of said further weight movement, and responsive to impingement thereagainst of said weight.

BENJAMIN F. messes. 

